Many recently evaluated HIV vaccine immunogens are designed to induce cell mediated immunity (CMI); however, studies suggest that a successful vaccine will require both strong CMI as well as neutralizing antibody responses. The potential efficacy of a neutralizing antibody response is supported by studies demonstrating that passive administration of neutralizing antibodies against HIV confers sterilizing immunity to pathogenic SHIV inoculation in animal models. Currently, there are five characterized, broadly neutralizing antibodies to HIV, three of which, antibodies 2F5, Z13, and antibody 4E10, recognize epitopes in the membrane proximal region of gp41. Antibody 2F5 recognizes the epitope ELDKWAS corresponding to residues 662-668 in the HIV HXB2 envelope protein. To date, attempts at expressing this epitope as part of a vaccine in to elicit 2F5-like antibodies have been unsuccessful. This suggests that the 2F5 epitope may be a conformation dependent structure that is poorly represented by soluble peptides or by monomeric gp41. It is widely believed that a successful humoral immunogen will have to present epitopes in the context of trimeric envelope proteins. Further, antibody binding studies suggest that the conformation of gp41 present during the formation of the "prefusogenic complex" may best represent the 2F5 epitope. The goal of this proposal is to develop an HIV vaccine with the potential to induce 2F5-like antibodies while providing potent CMI responses. We present a series of HIV gp41 vaccine constructs designed to present the ELDKWAS epitope as trimer mimicking the "prefusogenic-complex." These designs attempt to enhance the oligomerization and membrane expression levels of the encoded protein. We then plan to express these proteins along with HIV Gag, first using a novel dual promoter plasmid, and then using a dual promoter baculovirus expression system for high-level independent gene expression. This dual expression will result in engineered HIV viral-like particles (VLP) expressing the novel glycoprotein immunogens. HIV VLPs are capable of presenting oligomeric functional HIV envelope proteins on their surface. We plan to test the immunogenicity of these particles in the Balb/c mouse and guinea pig to assess CMI and neutralizing antibody responses, respectively. If successful, this design could serve as the foundation for a broadly applicable HIV vaccine.